Regulation of Aromatic Metabolism in the Fungi: Metabolic Control of the 3-Oxoadipate Pathway in the Yeast Rhodotorula mucilaginosa

Abstract

SUMMARYThe metabolic control of the protocatechuate branch of the 3-oxoadipate pathway in Rhodotorula mucilaginosa was examined and the specific inducers identified using appropriately blocked mutants. Three successive inductive events permitted the synthesis of the five enzymes converting p-hydroxybenzoate to 3-oxoadipyl-CoA: the independent induction of 4-hydroxybenzoate 3-monooxygenase by its own specific substrate, the independent induction of protocatechuate 3,4-dioxygenase by either protocatechuate or p-hydroxybenzoate, and finally the co-ordinate induction of 3-carboxymuconate cyclase, 3-carboxymuconolactone hydrolase and 3-oxoadipate CoA-transferase by either protocatechuate or p-hydroxybenzoate. Evidence is presented which suggests that R. mucilaginosa is unable to metabolize catechol or its usual precursors, and the significance of this is discussed in relation to control of the protocatechuate branch and the differing control mechanisms governing the synthesis of enzymes of the 3-oxoadipate pathway in other fungi and bacteria.

Base-Catalyzed Depolymerization of Solid Lignin-Rich Streams Enables Microbial Conversion

“…52 This organism appears to express proteins belonging to the protocatechuate branch of the β-ketoadipate degradation pathway but lacks enzymes of the catechol branch, and it is therefore unable to metabolize catechol. 53 One drawback for this organism is that there are few genetic tools currently available for red yeasts compared to P. putida and C. glutamicum, and therefore a more extensive effort is required to pursue genetic engineering strategies in this organism.…”

Regulation of Aromatic Metabolism in Fungi: Selection of Mutants of the Yeast Rhodotorula mucilaginosa with Nystatin

“…Preparation of cell-free extracts and measurement of the relevant enzymes are described in detail in the following paper (Cook & Cain, 1974 Preparation of nystatin. Nystatin (Nystan, E. R. Squibb & Sons, Liverpool) was prepared as a suspension in water at 2 mg/ml and the pH adjusted to 8-5 with 5 M-NaOH.…”

Phenol degradation by yeasts isolated from industrial effluents.

“…Some filamentous fungi (Jones et al, 1995), algae (Semple and Cain, 1996), and higher plants (Prasad and Ellis, 1978) have been reported to be able to degrade phenol. Reports on the decomposition of phenolic compounds by yeasts are scanty when compared to those on bacteria (Anderson and Dagley, 1980;Cook and Cain, 1974;Gaal and Neujahr, 1981;Hirayama et al, 1994;Hofmann and Vogt, 1987) and in all of the cases reported, the utilization of phenols was limited and slow. Middelhoven (1993) has made an extensive study on the metabolism of aromatic compounds by ascomycetous and basidiomycetous yeasts and yeastlike fungi, and demonstrated that the catechol branch of the 3-oxoadipate pathway and its hydroxyhydroquinone variant were involved in phenol and resorcinol catabolism of ascomycetes as well as of basidiomycetes.…”